A Y-associated allele is shared among a few ethnic groups of Asia

Climatic influence on the reproductive characteristics of Japanese males

We previously performed a survey of the sperm characteristics of the partners of pregnant women in four cities in Japan. In the present study, we analyzed the sperm characteristics of these subjects and the correlations between these sperm characteristics and climatic changes or Y chromosome haplogroups. Our results showed that more haplogroup D2a1 males than O2b1 males were born in the first half of the year (January to June), whereas more O2b1 males were born in the last half of the year (July to December) (P<0.05). This was agreed and correlated with the seasonal variations in their mean sperm concentrations. The haplogroup C, D* and D2a1 males displayed lower sperm concentrations from March to May, followed by an increase in their sperm concentrations starting in June or July, while the O2b1 males displayed higher sperm concentrations in the first half of the year followed by a sudden decrease from July to August (P<0.05). We hypothesize that the Japanese climate has different effects on the sperm characteristics and reproductive seasonality of males from different lineages; and therefore, has influenced the modern population of Japan.

High frequencies of Y-chromosome haplogroup O2b-SRY465 lineages in Korea: a genetic perspective on the peopling of Korea

Background

Koreans are generally considered a Northeast Asian group, thought to be related to Altaic-language-speaking populations. However, recent findings have indicated that the peopling of Korea might have been more complex, involving dual origins from both southern and northern parts of East Asia. To understand the male lineage history of Korea, more data from informative genetic markers from Korea and its surrounding regions are necessary. In this study, 25 Y-chromosome single nucleotide polymorphism markers and 17 Y-chromosome short tandem repeat (Y-STR) loci were genotyped in 1,108 males from several populations in East Asia.

Results

In general, we found East Asian populations to be characterized by male haplogroup homogeneity, showing major Y-chromosomal expansions of haplogroup O-M175 lineages. Interestingly, a high frequency (31.4%) of haplogroup O2b-SRY465 (and its sublineage) is characteristic of male Koreans, whereas the haplogroup distribution elsewhere in East Asian populations is patchy. The ages of the haplogroup O2b-SRY465 lineages (~9,900 years) and the pattern of variation within the lineages suggested an ancient origin in a nearby part of northeastern Asia, followed by an expansion in the vicinity of the Korean Peninsula. In addition, the coalescence time (~4,400 years) for the age of haplogroup O2b1-47z, and its Y-STR diversity, suggest that this lineage probably originated in Korea. Further studies with sufficiently large sample sizes to cover the vast East Asian region and using genomewide genotyping should provide further insights.

Conclusions

These findings are consistent with linguistic, archaeological and historical evidence, which suggest that the direct ancestors of Koreans were proto-Koreans who inhabited the northeastern region of China and the Korean Peninsula during the Neolithic (8,000-1,000 BC) and Bronze (1,500-400 BC) Ages.

Identification of novel allele on the locus 47z (DXYS5) in the Korean population

Two homogenous sequences of 47z (DXYS5) are located on the X (DXYS5X) and Y (DXYS5Y) chromosomes, and these are known to be useful polymorphic markers for tracing male-specific gene flow such as the migration routes of human populations. Using the 47z/StuI PCR-RFLP system, we found a novel allele which showed two bands, in contrast to the previous two allele types, one band (Y1) and three bands (Y2). This means that copies of PCR products derived from both the DXYS5X and DXYS5Y loci were clearly cut by the StuI enzyme, implying that the DXYS5X locus of the X chromosome is polymorphic. Allelic frequencies examined in 267 male Korean individuals showed that 95.8% had Y1, 3.4% Y2, and 0.8% had the novel allele. Our findings should contribute to a better understanding of genetic polymorphism on X and Y chromosomes, the molecular evolution mechanism of sex chromosomes, and how the migration route of Koreans is related to those of other East Asian populations.

Y-chromosomal DNA haplogroups and their implications for the dual origins of the Koreans

We have analyzed eight Y-chromosomal binary markers (YAP, RPS4Y(711), M9, M175, LINE1, SRY(+465), 47z, and M95) and three Y-STR markers (DYS390, DYS391, and DYS393) in 738 males from 11 ethnic groups in east Asia in order to study the male lineage history of Korea. Haplogroup DE-YAP was found at a high frequency only in Japan but was also present at low frequencies in northeast Asia, including 2.5% in Korea, suggesting a northern origin for these chromosomes. Haplogroup C-RPS4Y(711) was present in Korea and Manchuria at moderate frequencies: higher than in populations from southeast Asia, but lower than those in the northeast, which may imply a northern Asian expansion of these lineages, perhaps from Mongolia or Siberia. The major Y-chromosomal expansions in east Asia were those of haplogroup O-M175 (and its sublineages). This haplogroup is likely to have originated in southern east Asia and subsequently expanded to all of east Asia. The moderate frequency of one sublineage in the Koreans, haplogroup O-LINE1 (12.5%), could be a result of interaction with Chinese populations. The age of another sublineage, haplogroup O-SRY(+465), and Y-STR haplotype diversity provide evidence for relatively recent male migration, originally from China, through Korea into Japan. In conclusion, the distribution pattern of Y-chromosomal haplogroups reveals the complex origin of the Koreans, resulting from genetic contributions involving the northern Asian settlement and range expansions mostly from southern-to-northern China.

Human evolution and the Y chromosome

The past two years have seen the increased study of Y-chromosome polymorphisms and their relationship to human evolution and variation. Low Y-chromosome sequence diversity indicates that the common ancestor of all extant Y chromosomes lived relatively recently and the consensus of estimates of time to the most recent common ancestor concur with estimates of the mitochondrial DNA ancestor; but we do not know where this 'Adam' lived. Though the reason for low nucleotide diversity on the Y-chromosome remains unresolved, some of the mutations are proving highly informative in tracing human prehistoric migrations and are generating new hypotheses on human colonizations and migrations. The recent discovery of highly polymorphic microsatellites on the Y offers new possibilities for the investigation of more recent human evolutionary events, including the identification of male founders.

Long Y-associated (GATA)n alleles were observed in a few ethnic groups in Asia

A Y-associated polymorphic locus, DYS19, was analyzed in a few ethnic groups in Asia and compared with that in Caucasians and Negroes. The locus contains 4-nucleotide repeats, (GATA)n, and the length of the repeated segments can be determined by the polymerase chain reaction (PCR). The predominant allele was 202 bp followed by 198 bp in all the 3 Asian populations examined. Long repeats that were rare in other populations were found more frequently in these Asian populations.

Fathers and sons: the Y chromosome and human evolution

It should be possible to use Y chromosome DNA polymorphisms to trace paternal lineages for evolutionary and other studies, but progress in these areas has been slow because it has been difficult to find suitable markers. However, it is now possible to use selected, slowly evolving polymorphisms to draw a rudimentary Y chromosome tree, while more rapidly evolving polymorphisms allow most independent Y chromosomes to be distinguished. Different populations often have characteristically different Y chromosomes, and Y chromosome studies are soon likely to make a major contribution to our understanding of the origins of modern humans.